Rep. Paul Ryan, the Republican vice presidential candidate, channeled former President Ronald Reagan at a campaign stop in Ohio on Tuesday, telling crowds that voters are doing worse today than they were when President Obama entered office four years ago and when former President Jimmy Carter was in office.

Campaigning in the Cleveland suburbs, Mr. Ryan, of Wisconsin, said that the “Are You Better Off?” message that Mr. Reagan employed against Mr. Carter in the 1980 presidential race works just as well, if not better, against Mr. Obama today.

“Remember Ronald Reagan talking about Jimmy Carter? Are you better off now than you were four years ago?” Mr. Ryan said. “Well, you know what? We knew it then and we know it now. They fired Carter and they hired Reagan, and we are going to do the same thing this time.”

Mr. Ryan also planned to campaign in Cedar Rapids, Iowa, while GOP presidential nominee Mitt Romney traveled to the home of former Massachusetts Lt. Gov. Kerry Healy in Windsor, Vt., where he will prep for the debates with Mr. Obama.

The Democratic National Convention, meanwhile, got under way in Charlotte, N.C., on Tuesday. Mr. Carter is scheduled to address the audience via video, and first lady Michelle Obama will close out the evening after the keynote address by San Antonio Mayor Julian Castro.

Standing in front of a lectern with “Are You Better Off?” stripped across it, Mr. Ryan said, “Ohio is the epicenter” of the presidential election, before arguing that with the current unemployment rate, home mortgage delinquencies and bankruptcies, Mr. Obama’s record “is worse than Jimmy Carter’s record.”

“President Obama makes the Jimmy Carter years look like the good old days. If we fired JC then, why would we rehire BO now?” he said. “President Obama can tell you a lot — he is good at doing that — but he cannot tell you that you are better off.”